Spinning apparatus



Oct. 31, 1961 J. J. CALHOUN 3,006,028

SPINNING APPARATUS Filed May 25, 1959 Fig. 2.

2 Sheets-Sheet l INV EN TOR JAMES J. CALHOUN ATTORNEY Oct. 31, 1961 J. J. CALHOUN 3,006,028

SPINNING APPARATUS Filed May 25, 1959 2 Sheets-Sheet 2 Fig.5 Fig.6

/I[/ y Vflw Fig. 7 Fig. 30

I VENTOR JAMES J. HOUN ATTORNEY 3,006,028 SPENNENG APPARATUS Harries J. Calhoun, Wayneshore, Van, assignor to E. I. du Pont de Nemours and Company, Wilmington, Deli, a corporation of Delaware Filed May 25, 1959, Ser. No. 815,705 8 Claims. (Cl. 183) This invention relates to apparatus for producing artificial fibers of composite character which exhibit a high degree of uniformity in component distribution between individual fibers. More particularly, this invention relates to an improved spinneret for producing such fibers.

Where it is desired to incorporate the separate characteristics of two individual polymeric species into one filamentary structure, it is frequently advantageous to spin the two polymeric species in such a way that each species remains separate and distinct within a different area of the fiber cross section. This is particularly true Where the differences in properties of the two species are such as to produce a crimped fiber when the two species are spun in eccentric relationship to each other. For example, when two polymeric species having different shrinkage characteristics appear in eccentric relationship to each other in a single fiber, that fiber will develop a desirable spiral-type crimp when it is treated under conditions which cause the two components to shrink.

Various embodiments of apparatus for producing composite or side-by-side fibers from two separate solutions or melts which are capable of forming fibers on evaporation, coagulation, or cooling are described in US. Patent 2,386,173. However, such apparatus has not proved to be satisfactory in providing fibers having a high degree of uniformity of distribution of components in the fiber structure. In addition, when a plurality of fibers is spun from a single spinneret, variations in the structure of the various fibers occur.

It is, therefore, an object of this invention to provide apparatus capable of producing two-component fibers which have uniform distribution of the components throughout the fiber structure. Another object of this invention is to provide apparatus capable of producing a plurality of two-component fibers which have uniform distribution of the components in each fiber. A further object of this invention is to provide a new and improved spinneret for producing such fibers.

The objects of this invention are accomplished by providing, in apparatus for producing composite fibers having means for forwarding a plurality of fiber-forming materials to a spinning head and means for maintaining a separation of said materials to a point adjacent the inlet side of orifices of a spinneret, an improvement which comprises a spinneret containing a plurality of spaced orifices having an elongated cavity surrounding the inlet side of each orifice, each orifice being centered in the base of said elongated cavity. By providing an orifice having the particular configuration of that of the present invention, it has been found that a high degree of uniformity of distribution of the components appears in fibers extruded through the orifice. Separators or septa are used to provide separate zones for the fluid materials adjacent to the spinneret. The separators are positioned so that the cavity is essentially symmetrically displaced about its minor dimension in adjoining zones.

The cross-sectional area of the cavity should be between about five and twenty-five times the area of the orifice at the point where the fluid material issues from the spinneret. The long dimension of the cavity should be essentially perpendicular to the fluid interface, or septa, and should be at least about twice the width of the cavity in the plane of the inner surface of the spinneret. The exit orifice should be centered within the cavity.

3,lii 6,028 Patented Qct. 31,1961

The invention will be further illustrated by reference to the accompanying drawings in which:

FIGURE 1 is a vertical sectional view of one form of apparatus embodying the spinneret of this invention;

FIGURE 2 is a cross-sectional view of FIGURE 1 taken along the line 2--2;

FIGURE 3-a is a vertical cross-sectional view taken along the long dimension of the cavity surrounding the spinneret orifice; Y

FIGURE 3-b is a vertical cross-sectional view of the spinneret orifice of FIGURE 3-a taken along the short dimension of the cavity;

FIGURE 3-0 is a plan view of the spinneret orifice of FIGURES 3-a and 3-b;

FIGURES 4-a, 4b, and 4c are corresponding vertical cross-sectional and plan views of an alternate configuration for the spinneret of this invention; and

FIGURES 5, 6, and 7 are cross-sectional and plan views of other embodiments of spinneret orifices which may be used.

Referring to FIGS. 1 and 2, reference numeral lit designates a spinneret having a plurality of orifices 11 spaced apart in rings concentric with the center 'of spinneret it). The spinneret id is attached to supply head 12 by means of retaining ring 13. A gasket 14, providing a liquid seal around the periphery of spinneret it is positioned between the spinneret and supply head 12. Back plate 15, which is spaced apart from supply head 12 by divider l6, encloses the divided cavity in supply head 12, thereby providing separate chambers 17 and 18. Annular separators or septa 25 divide the space between back plate 15 and spinneret it) into a plurality of separate zones A, B, C, and D. Conduits 23 and 24 are in communication with chambers 17 and 18, respectively, and with alternate zones between separators 25; The lower edge of separators 25 is positioned in close proximity to the inside face of spinneret 10 in a manner which essentially divides orifices 11. A distribution membrane 26 and a fine-mesh screen assembly 27 are positioned between back plate 16 and spinneret l0.

In operation, two separate spinning solutions or melts are fed through metering pumps, not shown, into threaded pipes 21 and 22. The fluid from pipe 21 passes through inlet port 19 into chamber 17 and thence through conduits 23 into zones B and D. The fluid then flows through openings 28 in distribution membrane 26 and then through screen assembly 27 to spinneret orifices 11. In a similar manner, the second fluid is metered to pipe 22 through inlet port 2%) to chamber 18 and then through conduits 24 to zones A and C. The fluid fiows through openings 28 in distribution membrane 26 and then through screen assembly 27 to orifices 11. The fluids from alternate zones meet at orifices 11, thereby providing a liquid interface. The depending edges of separators 25 and orifices 11 are positioned in such a man-' her that the liquid interface is centered along line 33 as shown in FIG. 3a.

Referring again to FIG. 3-11, it will be noted that the elongated cavity which surrounds orifice .11 will be essentially symmetrically displaced in adjacent zones.

Referring to FIGS. 3-a to 7, inclusive, it will be apparent that a wide variety of spinneret orifice configurations are encompassed by the present invention. As previously indicated, the long dimension of the cavity is displaced in a direction essentially perpendicular to the depending edge of the separators or septa 25. The long dimension should be at least about twice the width of the cavity in the plane of the upper surface of spinneret 10.

As shown in FIGS. 3-b and 4-12, the cross-sectional shape of the cavity may be rectangular, or, as shown in FIG. 6, the cross-sectional area may be trapezoidal; It

'5 may likewise be triangular, semicircular, parabolic, or of a curved configuration, as shown in FIGURE 5, having two essentially straight sides. As shown in FIGS. 4-a, 4-b, and 4-c, the cavity may communicate with the orifice through a frustro-conical section.

As previously indicated, the cross-sectional area of the cavity taken along the narrow dimension should be between five and twenty-five times the area of the orifice at the point where the solution or melt issues from the spinneret. Preferably, this area is between ten and twenty times the area of the orifice exit.

The thickness of the spinneret is not critical. The diameter and length of the exit and of the orifice will depend on the material being spun and on the spinning conditions, and can be readily selected by those skilled in the art. Generally, diameters between about 0.004 inch and 0.012 inch are most useful, with the length of the exit end of the orifice generally being between one and three times its diameter. In determining the length of the exit end of the orifice, the frustro-conical section, as shown in FIG. 4b, would be disregarded.

In order to demonstrate any significant advance achieved in using the improved spinneret of the present invention, the following illustrative experiment was conducted.

Example A 25% solution of an acrylonitrile homopolymer of intrinsic viscosity 2.0 was prepared in dimethylformamide according to the process of Houtz as described in US. Patent 2,404,713. in a separate vessel, a 25% solution in dimethylformamide of a copolymer of 97% acrylonitrile and 3% sodium styrenesulfonate was prepared. This copolymer had an intrinsic viscosity of 1.5. The two solutions were separately filtered and pumped by positive displacement pumps through the separate inlets of apparatus of the type shown in FIG. 1. The pumping rates used for the two solutions were identical.

In the first experiment, the spinneret used contained orifices of the type shown in FIGS. 4-a, 4-17, and 4-c. The spinneret contained 84 orifices in each of three annular rings. As shown in FIGS. 4-a and 4-b, each orifice was provided with a rectangular cavity in which the dimension X was 0.090 inch, the dimension Y was 0.040 inch, and the dimension Z was 0.013 inch. The cylindrical orifice of the spinneret had a diameter U of 0.007 inch and a height V of 0.014 inch. The spinneret itself had a thickness of 0.060 inch. The frustro-conical part of the cavity thus had a height W of 0.033 inch. It had the same diameter U as the spinneret orifice at its lower extremity and the same diameter as the dimension Y at its upper extremity.

The two solutions were spun through this spinneret into an evaporative atmosphere under conditions normally used for the spinning of acrylonitrile fibers. The spun fibers were cross-sectioned and dyed at the boil for fifteen minutes in an aqueous solution containing an ex cess of the dye Brilliant Green Crystals (Color Index 662). The fibers were then observed under a microscope. According to visual observation, it was apparent that approximately 50% of the area of each fiber contained dye. Photomicrographs of the dyed fibers were made and were measured to determine the area of dyed and undyed parts of each fiber. It was found that half of the fibers contained between 40% and 60% of each of the two components, according to the dyeability test which is based on the rapid pickup of dye of the copolymer and almost negligible pickup of dye by the homopolymer. Every fiber contained at least 30% of each component so that there were no fibers present made up of only one polymeric species.

In a second test, the spinneret used contained outlet orifices of a diameter the same as that of the spinneret described above. The inlet cavity for each orifice was cylindrical with a diameter of 0.040 inch and a height of 0.013 inch, and a frustro-conical section connected the inlet and outlet. The same spinning solutions previously described were spun through this spinneret, and the yarns were precessed and dyed as indicated in the previous test. According to photomicrographs of the dyed fibers, 30 to 40% of the fibers contained less than 30% of one or the other of the two polymeric components, and 10% to 20% of the fibers containedonly one of the two components.

In a third part of the experiment, a spinneret was used containing orifices having a cylindrical cavity of 0.125 inch diameter. The height of this cavity and the dimensions of the exit orifice were identical with those of the earlier parts of the example. The two cylindrical portions were again connected by a frustro-conical section having top and bottom diameters equal to the diameters of the cylinders it connected. When fibers were produced with this spinneret, they were found to be no better in component distribution than those prepared with the spinneret having smaller cylindrical cavities.

It is thus apparent that a highly significant improvement in component distribution is realized by the use of a rectangular cavity as opposed to that obtained with the usual round cavity, even when the diameters of the latter are greater than the larger dimensions of the rectangular cavity.

Various modifications of the apparatus shown in FIGS.

1 and 2 may be used in combination with the spinneret of the present invention. For example, it is not necessary that the separators. or septa be in the form of concentric rings as shown in the drawings. They may be in the form of spokes of a wheel as illustrated in FIGS. 7, 8, and 9 of U.S. Patent 2,386,173. In utilizing this modification, the long dimension of the spinneret cavity will be in the direction perpendicular to the septum rather than in a direction essentially perpendicular to a tangent to the concentric septum illustrated in FIGS. 1 and 2 of the present drawing. The long dimension of the cavity must be in a direction such that the cavity is essentially symmetrically displaced in adjacent zones.

The number of septa is likewise not critical. Howeve it has been found that the improved spinneret of this invention provides the greatest improvement in uniformity of the distribution of components in apparatus having a plurality of concentric septa.

In designing such apparatus, care must be taken to provide a relatively constant pressure in each of the adjacent zones. For example in FIG. 1, when the solution from chambers 17 and 18 passes through a relatively small number of openings such as 23 and 24, the corrugated perforated plate of distribution membrane 26 serves to equalize the pressure of the fluid material around the complete circumference of each ring of holes. Such a distribution membrane is suitably fabricated from stainless steel, and preferably has approximately the same number and size of orifices as the spinneret itself,

In spinneret assemblies having a number of concentric septa, the spinneret may be cup-shaped as shown in the drawings, or may be in the form of a flat plate. The

V spinneret may be supported at its center as Well as around its periphery. Suitable gaskets must, of course, be provided to prevent leakage. If additional filtration of the spinning solutions or melts is desired, chambers 17 and 18 may be provided with filtering material.

The materials of construction of the spinneret and the spinneret assembly are not critical and may be selected from any materials that are known to be satisfactory for the spinning of both of the solutions or melts used. In the case of acrylonitrile polymers, it is generally desirable to use apparatus constructed of Type 316 stainless steel because this material shows a very low degree of corrosion under operating conditions.

The apparatus of this invention is useful wherever it is desired to produce composite fibers of two components having a high degree of uniformity with regard to the amount of each component present in each fiber. Among the most useful species of such composite fibers are those having a relatively large difierence in content of highly ionic materials such as sodium styrenesulfon-ate comonomer between the two components. The difierence in amount of this material between the two parts of the fiber is responsible for the development of desirable crimp within the fiber. The presence of this modifier likewise imparts dyeability to the fiber. When the distribution of the two components is erratic from fiber to fiber, the resulting fibers will be noticeably variable with regard both to crimp and to dyeability. If some fibers are produced which contain essentially no polymer having styrenesulfonate, these fibers will have essentially no crimp and will have essentially no dyeability. If fibers are produced containing only the polymer which is modified with the styrenesulfonate, these fibers will show a high degree of dyeability, but will again be without crimp. Therefore, it is essential for the production of uniform, useful fibers that the distribution of components within the individual fibers be as uniform as possible. Such uniformity is effected with the apparatus of this invention.

It will be apparent that many widely different embodiments of this invention may be made Without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. In apparatus for producing composite fibers comprising means for forwarding a plurality of fiber-forming materials to a spinning head and means for maintaining a separation of said materials to a point adjacent the inlet side of the orifices of a spinneret, the improvement which comprises a spinneret containing a plurality of spaced cylindrical orifices having an elongated cavity surrounding the inlet side of each orifice, each orifice being centered in the base of said elongated cavity, said elongated cavity having its major dimension in a plane essentially parallel to the surface of the inlet side of said spinneret with said separation means bisecting the major dimension of said elongated cavity to provide separate zones at each side of said orifice.

2. The apparatus of claim 1 wherein said cavity is essentially rectangular in shape.

3. The apparatus of claim 2 wherein the cross-sectional area of said cavity is between about five and twenty-five times the area of the orifice exit, and the length of said cavity is at least about two times its width.

4. The apparatus of claim 1 wherein said on'fice and said cavity are in communication with a frustro-conical channel which is centered in the base of said elongated cavity.

5. In apparatus for producing composite fibers comprising a spinning head having separate chambers therein, a spinneret having a plurality of orifices, said spinneret being spaced apart from said spinning head, septa dividing the space between said spinneret and said chambers into a plurality of separate zones with adjoining zones being in communication with each other at a point contiguous to at least one of said orifices, conduit means for forwarding fiber-forming materials from each of said separate chambers to adjoining zones thereby providing an interface between said materials at said orifices, the improvement which comprises a spinneret containing a plurality of cylindrical orifices, an elongated cavity surrounding the inlet side of each of said orifices, each orifice being centered in the base of said elongated cavity, said cavity being in communication with two adjoining zones and essentially symmetrically displaced about its minor axis in each of said adjoining zones, said cavity having its major dimension in a plane essentially parallel to the surface of the inlet side of said spinneret.

6. The apparatus of claim 5 wherein said cavity is essentially rectangular in shape.

7. The apparatus of claim 6 wherein the cross-sectional area of said cavity is between about five and twenty-five times the area of the orifice exit and the length of the cavity is at least about two times its width.

8. The apparatus of claim 5 wherein said orifice and said cavity are in communication with a frustro-conical channel which is centered in the base of said elongated cavity.

References Cited in the file of this patent UNITED STATES PATENTS 1,964,659 Brumberger June 26, 1934 2,386,173 Kulp et al. Oct. 2, 1945 2,517,711 Pool et a1 Aug. 8, 1950 2,742,667 Cluzeau et al Apr. 24, 1956 FOREIGN PATENTS 755,342 France Sept. 4, 1933 

